The present invention relates to an arrangement for plausibility checking of a rollover decision in a motor vehicle, with one or more yaw rate sensors and/or acceleration sensors detecting movements of the vehicle and a processor deriving a decision from the sensor signals as to whether the vehicle movements will result in a rollover, and with an arrangement being present which, from measured accelerations in the direction of the vertical axis and transverse axis of the motor vehicle, forms a criterion for plausibility checking of a rollover decision which has been made.
An arrangement is known from German Published Patent Application No. 197 44 083 which generates a trigger signal for restraint devices in the motor vehicle when, on the basis of measured yaw rates and/or accelerations, it recognizes an imminent rollover event of the motor vehicle. If a rollover of a vehicle is going to occur, all of the passenger protection devices installed in the vehicle, such as the roll bar, seat belt tightening system, airbags, etc., must be deployed at the correct time. In order that all of these protective devices can be deployed at the correct time, it must be recognized as early as possible whether movements of the motor vehicle, e.g., rotations around its longitudinal axis, its transverse axis, or its vertical axis, will result in a rollover. The restraint devices in the vehicle are also to be deployed only if a rollover of the vehicle actually occurs.
In order to avoid incorrect rollover decisions and thus incorrect deployments of restraint devices, every rollover decision is subjected to a plausibility check according to German Published Patent Application No. 197 44 083. Errors in a rollover decision could, for example, occur because yaw rate and/or acceleration sensors or a processor in which the rollover decision is produced operate incorrectly. According to German Published Patent Application No. 197 44 083, the plausibility check occurs in that two rollover decision criteria are produced and an imminent rollover event is signaled and deployment of restraint devices occurs only if both decision criteria are received simultaneously. The first rollover decision criterion is produced solely from the yaw rates of the motor vehicle around its longitudinal, transverse, and vertical axes. The second decision criterion is derived from measured accelerations in the direction of the three vehicle axes, with first the tilt angle of the vehicle around its longitudinal and transverse axes being calculated from the measured accelerations and this tilt angle being subjected to a threshold decision. Nothing is stated about the process of the threshold decision in this publication.
The present invention has as its object the provision of an arrangement of the type initially described which performs a plausibility check of a rollover decision which is as reliable as possible at low cost.
The object stated is achieved that an arrangement is present which signal the plausibility of the rollover decision if the acceleration measured in the direction of the vertical axis is either greater than a preset upper threshold or less than a preset lower threshold, or if the acceleration measured in the direction of the vertical axis is between the two thresholds, but the acceleration measured in the direction of the transverse axis simultaneously exceeds a threshold which depends on the acceleration measured in the direction of the vertical axis.
According to the present invention, a reliable plausibility criterion for a rollover decision is derived solely from the accelerations measured in the direction of the vertical axis and the transverse axis of the vehicle.
Therefore, either the threshold for acceleration in the direction of the transverse axis associated with each acceleration value in the direction of the vertical axis can be stored in a table or the acceleration threshold in the direction of the transverse axis can be calculated from the current acceleration measured in the direction of the vertical axis according to a predefined algorithm.
The threshold for the acceleration in the direction of the transverse axis is preferably an acceleration measured in the direction of the longitudinal axis of 1 g (g is acceleration due to gravity), and the threshold for the acceleration in the direction of the transverse axis declines to a value less than 1 g with acceleration in the direction of the vertical axis increasing from 1 g to 3 g and decreasing from 1 g to 0.2 g.